Safe Haskell | None |
---|---|

Language | Haskell2010 |

Functions and instances relating to unification

## Synopsis

- freshType :: MonadState CheckState m => m SourceType
- solveType :: (MonadError MultipleErrors m, MonadState CheckState m) => Int -> SourceType -> m ()
- substituteType :: Substitution -> SourceType -> SourceType
- unknownsInType :: Type a -> [(a, Int)]
- unifyTypes :: (MonadError MultipleErrors m, MonadState CheckState m) => SourceType -> SourceType -> m ()
- unifyRows :: forall m. (MonadError MultipleErrors m, MonadState CheckState m) => SourceType -> SourceType -> m ()
- alignRowsWith :: (Type a -> Type a -> r) -> Type a -> Type a -> ([r], (([RowListItem a], Type a), ([RowListItem a], Type a)))
- replaceVarWithUnknown :: MonadState CheckState m => Text -> SourceType -> m SourceType
- replaceTypeWildcards :: (MonadWriter MultipleErrors m, MonadState CheckState m) => SourceType -> m SourceType
- varIfUnknown :: SourceType -> SourceType

# Documentation

freshType :: MonadState CheckState m => m SourceType Source #

Generate a fresh type variable

solveType :: (MonadError MultipleErrors m, MonadState CheckState m) => Int -> SourceType -> m () Source #

Update the substitution to solve a type constraint

substituteType :: Substitution -> SourceType -> SourceType Source #

Apply a substitution to a type

unknownsInType :: Type a -> [(a, Int)] Source #

Compute a list of all unknowns appearing in a type

unifyTypes :: (MonadError MultipleErrors m, MonadState CheckState m) => SourceType -> SourceType -> m () Source #

Unify two types, updating the current substitution

unifyRows :: forall m. (MonadError MultipleErrors m, MonadState CheckState m) => SourceType -> SourceType -> m () Source #

Unify two rows, updating the current substitution

Common labels are identified and unified. Remaining labels and types are unified with a trailing row unification variable, if appropriate.

alignRowsWith :: (Type a -> Type a -> r) -> Type a -> Type a -> ([r], (([RowListItem a], Type a), ([RowListItem a], Type a))) Source #

Align two rows of types, splitting them into three parts:

- Those types which appear in both rows
- Those which appear only on the left
- Those which appear only on the right

Note: importantly, we preserve the order of the types with a given label.

replaceVarWithUnknown :: MonadState CheckState m => Text -> SourceType -> m SourceType Source #

Replace a single type variable with a new unification variable

replaceTypeWildcards :: (MonadWriter MultipleErrors m, MonadState CheckState m) => SourceType -> m SourceType Source #

Replace type wildcards with unknowns

varIfUnknown :: SourceType -> SourceType Source #

Replace outermost unsolved unification variables with named type variables